1. Field of the Invention
The present invention is related to a terminal-to-terminal (inter-terminal) communication connection control method using an IP (Internet Protocol) transfer network, which is applicable to an IP communication established between two terminal units such as an IP terminal, an IP telephone, and a voice/image apparatus (audio/visual apparatus), and also applicable to a 1:n type IP Communication utilizing a multicast IP technique.
2. Description of the Prior Art
As a method capable of realizing various terminal-to-terminal communications such as mail transmissions/receptions, telephone, and image communications while an IP transfer network is utilized, Japanese Patent Application No. 128956/1999 (will be referred to as a “prior patent application” hereinafter) has been filed by the Applicant. This prior patent application discloses the method of realizing “integrated IP transfer network” containing therein a plurality of IP transfer networks having various characteristics, while separating these IP transfer networks. These IP transfer networks are known as an IP telephone network, an IP image network, and IP electronic data general-purpose network. To realize the IP transfer network for uniting various sorts of terminal-to-terminal communications, contents disclosed by the above-explained prior patent application will now be briefly explained with reference to FIG. 1.
Inside integrated IP transfer network 901, a plurality of IP transfer networks having different characteristics such as the IP image network 902, the IP electronic data general-purpose network 903, and the IP telephone network 904 are virtually installed. While the address management tables are set inside the network node apparatus 905-X and the network node apparatus 905-Y, which are provided at the input points to the integrated IP transfer network 901 from the external unit for the integrated IP transfer network 901, the address of the terminal unit is previously registered into the address management table. Since the address written into the IP packet entered into the integrated IP transfer network 901 is compared with the address registered in the address management table, the IP packets can be transmitted, while these IP packets are separated to the individual IP transfer networks within the integrated IP transfer network 901.
Next, in connection with the present invention, the terminal-to-terminal communication connection control method (No. 7-common line signal system) employed in a public switched telephone network (PSTN) will now be simply explained.
In FIG. 2, reference numerals 98-1 and 98-3 show exchangers (subscriber exchangers) to which telephone sets are connected, reference numeral 98-2 indicates a relay exchanger, and also reference numerals 98-4 and 98-5 represent telephone sets. Reference numerals 98-6 to 98-8 show communication path control units of the exchangers, reference numerals 98-9 to 98-11 indicate internal control units of the exchangers, and also reference numerals 98-12 to 98-14 indicate signalling points for controlling terminal-to-terminal connections of telephone sets. The internal control units of the exchangers perform information exchanges used to set/recover communication lines between the communication path control units and the signalling points in conjunction with the internal operation controls of the exchangers.
In particular, reference numerals 98-12 and 98-14 will be referred to as signalling end points (SEP). More specifically, reference numeral 98-13 is called as a signalling transfer point (STP). Also, reference numeral 98-15 denotes another signalling end point. These signalling end points 98-12 to 98-15 are connected via signal lines 98-24 to 98-27 to a signal network 98-16. While information used to control terminal-to-terminal communication connections and also execute maintenance/operations of networks is stored into a signalling unit (SU), these signalling end points 98-12 to 98-15 mutually transmit/receive the stored information to each other. A 16-bit point code (PC) is applied to one signalling end point in order to discriminate the own signalling end point from another signalling end point. On the other hand, reference numerals 98-21 to 98-22 show communication lines used to transfer telephone voice (speech), but not used to transfer information for controlling terminal-to-terminal communication connections. The telephone lines 98-20 and 98-23 correspond to interfaces (UNI) through which a combination between voice and control information of terminal-to-terminal communication connections is transferred in an integral form. Namely, both the voice and the control information of terminal-to-terminal communication connections are transferred through the interfaces without being separated from each other. The No. 7-common line signal system is featured by that the signal lines 98-24 to 98-26 are separated from the communication lines 98-21 and 98-22 inside the public switched telephone network (PSTN).
A signalling unit indicated in FIG. 3 contains a “destination point code (DPC)”, an “origin point code (OPC)”, a “circuit identification code (CIC)”, a “message type (MSG)” and a parameter of the message.
The destination point code shows a destination to which a signalling unit is transmitted, the origin point code indicates a transmission source of a signalling unit, and the circuit identification code represents an identification number for identifying a communication line set between a transmission source signal point and a destination signal point. As the message, for example, there are IAM, ACM, CPG, ANM, REL, RLC, SUS, RES and CON, which are used to control terminal-to-terminal communication connections. Such a signalling unit which is written as “IAM” into a message area of the signalling unit is referred to as an initial address message (IAM). Similarly, such a signalling unit which is written as “ACM” into the message area of the signalling unit is referred to as an address completion message (ACM), such a signalling unit which is written as “CPG” into the message area of the signalling unit is referred to as a call pass message (CPG), and also such a signalling unit which is written as “ANM” into the message area of the signalling unit is referred to as an answering message (ANM). Similarly, such a signalling unit which is written as “REL” into the message area of the signalling unit is referred to as a release message (REL), such a signalling unit which is written as “RLC” into the message area of the signalling unit is referred to as a release completion message (RLC), and also such a signalling unit which is written as “SUS” into the message area of the signalling unit is referred to as an interrupt message (SUS). Similarly, such a signalling unit which is written as “RES” into the message area of the signalling unit is referred to as a restart message (RES), and such a signalling unit which is written as “CON” into the message area of the signalling unit is referred to as a connection message (CON).
Referring now to FIG. 2, a description will be made of a method for controlling a terminal-to-terminal connection control by which a telephone communication is established from the telephone set 98-4 via the exchangers 98-1, 98-2, 98-3 to the telephone set 98-5, as shown in FIG. 2. It should be noted that the respective signalling points exchange such a signalling unit via the signal lines 98-24 to 98-27 and the common line signal network 98-16 to each other. In the signalling unit, the signalling point codes applied to the respective signalling points are set as addresses indicative of designations and transmission sources. The telephone set 98-4 is connected via the telephone line 98-20 to the exchanger 98-1. The terminal-to-terminal connection control of the telephone set 98-4 is loaded to the signalling point 98-12 within the exchanger 98-1. Similarly, the telephone set 98-5 is connected via the telephone line 98-23 to the exchanger 98-3. The terminal-to-terminal connection control of the telephone set 98-5 is loaded to the signalling point 98-14 within the exchanger 98-3.
When a user issues a call request from the telephone set 98-4, the signalling point 98-12 receives this call request (Step X1 of FIG. 4), and a communication line is determined by using a destination telephone number received from the telephone number 98-4 because of the functions of both the communication path control unit 98-6 and the exchanger internal control unit 98-9 of the exchanger 98-1. A signalling unit into which a circuit line identifier (CIC) of the determined communication line is written is formed as an initial address message (IAM). In the parameter area of the initial address message (IAM), at least the telephone number of the telephone set 98-5, namely a destination telephone number “Tel-No-98-5” is written. Furthermore, the telephone number of the telephone 98-4, namely, a telephone number of a transmission source “Tel-No-98-4” may be written thereinto.
Next, the signalling point 98-12 sends the initial address message (IAM) for issuing the telephone call to the signalling point 98-13 provided in the exchanger 98-2 (Step X2). The initial address message IAM contains a line number “98-4-98-5” of a communication line corresponding to the logic communication line inside the telephone communication line 98-21, the destination telephone number “Tel-No-98-5”, the transmission source telephone number “Tel-No-98-4” (omittable option), and the like. After the signalling point 98-12 has sent the IAM, the operation of the signalling point 98-12 is advanced to a waiting condition for an address completion message (ACM: will be explained later), and also initiates an ACM waiting timer.
The signalling point 98-13 provided within the exchanger 98-2 receives the above-explained IAM, and then notifies the line number “98-4-98-5” via the exchanger internal control unit 98-10 to the telephone communication line control unit 98-7. The telephone communication line control unit 98-7 executes a conducting test in order that the telephone communication line 98-21 can be used for the telephone communication. The signalling point 98-13 sends the IAM to the signalling point 98-14 provided in the exchanger 98-3 (step X3). The signalling point 98-14 checks the content of the received IAM in order that the telephone communication line 98-22 can be used for the telephone communication via the control unit 98-11 and the telephone communication line control unit 98-8. Furthermore, while the signalling point 98-14 connects the telephone set 98-5 to the exchanger 98-3, this signalling point 98-14 checks as to whether or not a call reception is permitted. When the call reception is allowed, the signalling point 98-14 issues a call setting request to the telephone set 98-5 (Step X4). Further, the signalling point 98-14 returns such an address completion message (ACM) which notifies that the IAM is received (Step X5). The ACM message is reached via the signalling point 98-13 to the signalling point 98-12 (Step X6). Upon receipt of the ACM message, the signalling point 98-12 stops the counting operation of the ACM waiting timer which has been set. In such a case that the counting operation of the ACM waiting timer is completed at a time instant before the ACM message is received, the telephone communication line is released.
When the signalling point 98-14 within the exchanger 98-3 receives information for implying such a fact that the calling request is being received from the telephone set 98-5 (Step X7), the signalling point 98-14 transmits the call pass message (CPG) to the signalling point 98-13 (Step X8). The signalling point 98-13 transmits the received CGP to the signalling point 98-12 (Step X9). The signalling point 9-12 within the switching point 98-1 receives the CPG message. Next, the signalling point 98-12 sends a calling sound to the telephone set 99-4 (Step X10). When the telephone set 98-5 responds to the above-described call setting request (Step X11), the telephone communication line 98-23 between the telephone set 98-5 and the exchanger 98-4 can be used for the telephone communication, and further the response message (ANM) for indicating that the telephone set 98-5 responds to the call setting request is sent to the signalling point 98-13 (Step X12).
The signalling point 98-13 transmits the received ANM to the signalling point 98-12 (Step X13), the signalling point 98-12 notifies stopping of the calling sound under transmission to the telephone set 98-4 (Step X14), and thus, telephone voice (speech) can be transmitted/received between the telephone set 98-4 and the telephone set 98-5. The operation is advanced to a telephone communication phase (Step X15). In the case that the handset of the telephone set 98-4 is put on (on-hook), the release request (REL) is sent out (Step X16), and the signalling point 98-12 receives the release request (REL), the signalling point 98-12 sends out a next release request (REL) to the signalling point 98-13 (Step X17), and furthermore, notifies to the telephone set 98-4, such a release completion (RLC) for indicating that the telephone communication line is brought into an empty state (Step X18). Then, upon receipt of the release request (REL), the signalling point 98-13 sends out the next release request (REL) to the signalling point 98-14 (Step X19), and further, notifies such a release completion (RLC) for indicating that the telephone communication line is brought into the empty state to the signalling point 98-12 (Step X20). Then, upon receipt of the release request (REL), the signalling point 98-14 sends out the next release request (REL) to the telephone set 98-5 (Step X21), and further, notifies such a release completion (RLC) for indicating that the telephone communication line is brought into the empty state to the signalling point 98-13 (Step X22). There are several variations in the sequential operations of the terminal-to-terminal communication connection controls which are transmitted/received between the telephone set 98-4 and the signalling point 98-12, and also between the signalling point 98-14 and the telephone set 98-15, depending upon sorts of telephone sets. For instance, a confirmation notification with respect to a release completion may be issued from the telephone set 98-4 to the signalling point 98-12 just after the above-explained Step X18. Alternatively, a confirmation notification with respect to the release completion may be issued from the signalling point 98-14 to the telephone set 98-5 just after the Step X23.
FIG. 5 is an explanatory diagram for explaining another control method for controlling terminal-to-terminal connections by which a telephone communication is made from the telephone set 98-4 via the exchanger 98-1 through the exchanger 98-3 to the telephone set 98-5. This terminal-to-terminal communication connection control method corresponds to such a communication connection control method made by eliminating the process operations defined at the Steps X5 and X6 (namely, by eliminating address completion message ACM) from the terminal-to-terminal communication connection control method as explained in FIG. 4. It should be understood that at the Step X2, the signalling point 98-12 sets the CPG waiting timer instead of the above-explained ACM waiting timer, and the signalling point 98-12 stops the CPG waiting timer after the Step X9. The above-explained terminal-to-terminal communication connection control method is such a control method applied to such a case that the exchanger is not an ISDN exchanger, but is an analog exchanger.
FIG. 6 is an explanatory diagram for explaining another method of controlling terminal-to-terminal communication connections between the telephone set 98-4 and the telephone set 98-5. This terminal-to-terminal communication connection control method corresponds to such a control method example that in the above-described terminal-to-terminal communication connection control method, a series of process steps for interrupting a telephone communication without waiting for the response completion message (Step X14) and the telephone communication phase (Step X15) is carried out (Step X16 to Step X23).
FIG. 7 is an explanatory diagram for explaining a further control method for controlling terminal-to-terminal communication connections by which a telephone communication is made from the telephone set 98-4 via the exchanger 98-1 through the exchanger 98-3 to the telephone set 98-5. This terminal-to-terminal communication connection control method corresponds to such a control method. That is, while a telephone communication is carried out (Step X15), the handset of the telephone set 98-4 is positioned only for a short time period (on hook), and an interrupt message is transmitted in order to temporarily stop the telephone communication (Steps X30 to X33). Then, the handset is returned to the original setting position (off hook), and the restart message for restarting the telephone communication is transmitted (Steps X35 to X38), and thus, the process operation is returned to the telephone communication (Step X39). The subsequent steps of the release (REL) and the release completion (RLC) are similar to those as explained with reference to FIG. 5 (Steps X40 to X47).
Next, with respect to the IP telephone communication, there is proposed “multimedia communication system based on JT-H323” of TTC standard, which is described in, for instance, ITU-T recommendation H323 ANNEX D regulation (version of April, 1999). The technical idea “SIGNALLING PROTOCOL AND PACKETING OF MEDIA SIGNAL” by which the call connections are controlled in the multimedia terminal-to-terminal communication is defined as JT-H225. Also, the technical idea “CONTROL PROTOCOL FOR MULTIMEDIA COMMUNICATION” in the multimedia terminal-to-terminal communication is defined as JT-H245.
Next, referring to FIG. 8 to FIG. 11, the basic functions of the JT-H323 gateway defined by ITU will be described. The present invention also refers to the basic functions.
In FIG. 8, a block 800 indicates the JT-H323 gateway. In this gateway 800, a voice (speech) signal and/or an image (picture) signal entered from an SCN line 801 is converted into a digital signal in an SCN terminal function 802, a data format and/or a signal transmission/reception rule is converted in a conversion function 803, and then, the data format is converted into the format of the IP packet in a terminal function 804. The resulting IP packet is sent out to an IP communication line 805. Also, as to a packet flow along an opposite direction, namely, an IP packet containing voice (speech) data and/or image data entered from the IP communication line 805 is decoded in a digital data format by the terminal function 804, and a data format and/or a signal transmission/reception rule are converted by the conversion function 803. The resultant digital data is converted into a signal flowing through the SCN line by the SCN terminal function 802 and sent to the SCN line 801. In this case, both a voice signal and an image signal may be separated into both “call control data” and “net data.” This call control data is used so as to send/receive a telephone number with respect to a communication third party. The net data constitutes voice and/or images itself. Through a communication line 805, an IP packet 810 (refer to FIG. 9) functioning as the call control data flows, an IP packet 811 (refer to FIG. 10) functioning as the net data which constitutes the voice itself flows, and an IP packet 812 (refer to FIG. 11) functioning as the net data which constitutes the image itself flows. In the case of an ISDN line, the SCN terminal function 802 corresponds to a data line terminating apparatus (DSU). Also, the terminal function 804 owns such a terminal communication function required for the bidirectional (interactive) communication between the JT-323 telephone set and the JT-323 voice/image apparatus.
Next, the integrated information communication network proposed in Japanese Patent No. 3084681-B2 closely related to the terminal-to-terminal communication connection control method of the present invention will now be briefly explained with reference to FIG. 12.
A block 191 shows an integrated IP communication network, an IP terminal 192-1 owns an IP address “EA01”, and another IP terminal 192-2 owns an IP address “EA02”. This example corresponds to such an example that an external IP packet 193-1 is transferred from the IP terminal 192-1 via the integrated IP communication network to the IP terminal 192-2. Both the IP addresses “EA01” and “EA02” are referred to as “external IP addresses”, since these IP addresses are used outside the integrated IP communication network 191. In FIG. 12 to FIG. 15, as to head portions of IPs, only IP address portions are described, and other items are omitted.
When the network node apparatus 195-1 receives the external IP packet 193-1, this network node apparatus 195-1 confirms that the internal IP address is equal to “IA01”, and the destination external IP address of the IP packet 193-1 is equal to “EA02”. The internal IP address is applied to the terminal unit (logic terminal) of the logic communication line 194-1 into which the IP packet 193-1 is entered. Then, the network node apparatus 195-1 retrieves the content of the address management table 196-1 shown in FIG. 12, and retrieves such a record in which the internal IP address of the transmission source is equal to “IA01” in the beginning, and thereafter, the destination external IP address is equal to “EA02”. Furthermore, the network node apparatus 195-1 checks as to whether or not the external IP address “EA01” of the transmission source within the IP packet 193-1 is contained in the previously detected record. It should be understood that such a check operation as to whether or not the external IP address “EA01” of the transmission source within the IP packet 193-1 is contained in the previously-detected record may be omitted.
In the present example, while it is such a record containing the IP addresses “EA01, EA02, IA01, IA02” on the second row from the top row, an IP packet 193-2 having such an IP header is formed (namely, IP packet is encapsulated) using the IP addresses “IA01” and “IA02” located inside the record. The IP header is such that the transmission source IP address is “IA01”, and the destination IP address is “IA02”. In this case, symbols “IA01” and “IA02” are called as internal IP addresses of the integrated IP communication network 191. The internal IP packet 193-2 is reached through the routers 197-1, 197-2 and 197-3 to the network node apparatus 195-2. The network node apparatus 195-2 removes the IP header of the received internal IP packet 193-2 (anti-encapsulation of IP packet), sends out the acquired external IP packet 193-3 to the communication line 194-2, and then, the IP terminal 192-2 receives the external IP packet 193-3. Is should also be noted that 197-6 is an example of such a server that the external IP address is “EA81”, and the internal IP address is “IA81”.
FIG. 13 indicates another embodiment of an address management table. That is, the address management table 196-1 of FIG. 12 is replaced by an address management table 196-3 of FIG. 13, the address management table 196-2 of FIG. 12 is replaced by an address management table 196-4 of FIG. 13, and other portions are identical to those of the above-explained address management table. The known address mask technique may be applied to the address management tables 196-3 and 196-4.
In the beginning, the record of the address management table 196-3 containing the internal IP address “IA01” is retrieved. This internal IP address is applied to the logic terminal of the terminal unit of the communication line 194-1. In this case, both the record of the first row at the record of the second row in the address management table 196-3 from the top row correspond to the records of interest. With respect to the record of the first row, a check is made as to whether or not an AND-gating result between a destination-use external IP mask “Mask81” and the destination external IP address “EA02” within the external IP packet 193-1 is coincident with a destination external IP address “EA81x” within the first row record (refer to the below-mentioned formula (1)). In this case, the AND-gating result is not coincident with the external IP address “EA81x”. With respect to the record of the second row, a check is made as to whether or not an AND-gating result between a destination-use external IP mask “Mask2” and the destination external IP address “EA02” within the external IP packet 193-1 is coincident with a destination external IP address “EA02y” within the second row record (refer to the below-mentioned formula (2)). In this case, the AND-gating result is coincident with the external IP address “EA02y”. Also, with respect to the transmission source IP address, a comparison is made in accordance with the below-mentioned formula (3) in a similar manner:If (“Mask81” and “EA02”=“EA81x”)  (1)If (“Mask2” and “EA02”=“EA02y”)  (2)If (“Mask1y” and “EA01”=“EA01y”)  (3)
Based upon the above-explained comparison result, the record of the second row is selected, and both the internal records “IA01” and “IA02” contained in the record of the second row are employed so as to perform the encapsulation, so that the internal IP packet 193-2 is formed. It should be noted that the comparison using above-mentioned formula (3) can not be made when the regions of both the transmission source external IP address and the address mask in the record of the address administration table 196-3 are omitted.
FIG. 14 indicates a further embodiment of an address management table. That is, the address management table 196-1 of FIG. 12 is replaced by an address management table 196-5 of FIG. 14, the address management table 196-2 of FIG. 12 is replaced by an address management table 196-6 of FIG. 14, and other portions are identical to those of the above-explained address management table. In this example, the address management tables 196-5 and 196-6 do not contain the transmission source external IP addresses, and the transmission source external IP address is not cited in the IP encapsulation. When the IP packet 193-1 is encapsulated, the destination internal IP address “IA02” is determined based upon the transmission source internal IP address “IA01” and the destination external IP address “EA02” inside the address management table 196-5.
FIG. 15 illustratively shows a further embodiment of the address management table. This embodiment corresponds to such an embodiment that the integrated IP communication network of FIG. 12 is replaced by an optical network, and the internal IP packet is substituted by an internal optical frame. This further embodiment will now be briefly explained. In this drawing, a block 191x indicates an IP packet transfer network, and also represents an optical network in which an IP packet is transferred by employing an optical frame. The optical frame is transferred to an optical communication path provided inside the optical network 191x. This optical communication path is equal to such a function of a communication-1 layer and a communication-2 layer. An optical link address is applied to a header portion of an optical frame. In such a case that the optical frame corresponds to an HDLC frame, the optical link address corresponds to an HDLC address employed in the HDLC frame.
An IP terminal 192-1x owns an IP address “EA1”, and another IP terminal 192-2x owns an IP address “EA2”. This example corresponds to such an example that an external IP packet 193-1x is transferred from the IP terminal 193-1x via the optical network 191x to the IP terminal 192-2x. In FIG. 15, only IP address portion is described as to a header portion of an IP, only header portion is similarly described as to an optical frame, and other items are omitted.
When the network node apparatus 195-1x receives the external IP packet 193-1x, this network node apparatus 195-1x confirms such a fact that an internal optical link address is equal to “IA1”, and an external destination IP address of the IP packet 193-1x is equal to “EA2”, and the internal optical link address is applied to a termination unit (logic terminal) of a logic communication line 194-1x into which the IP packet 193-1x is inputted. Then, the network node apparatus 195-1x retrieves a content of an address administration table 196-1x shown in FIG. 15, and also retrieves a record containing such addresses that an internal optical link address of a transmission source corresponds to “IA1” in the beginning, and subsequently, an external destination IP address corresponds to “EA2”. Furthermore, the network node apparatus 195-1 checks as to whether or not the transmission source external IP address “EA1” contained in the IP packet 193-1x is included in the above-detected record. Alternatively, the checking operation as to whether or not the transmission source external IP address “EA1” contained in the IP packet 193-1x is included in the detected record may be omitted.
In this example, while the record is equal to such a record containing addresses of “EA1, EA2, IA1, IA2” on the second column from the top column, an optical frame 193-2x is produced by employing to optical link addresses “IA1” and “IA2” present inside the record (namely, IP packet is capsulated). This optical frame 193-2x owns such a header that the optical link address of the transmission link address is “IA1” and the optical link address of the destination is “IA2”. In this case, symbols “IA1” and “IA2” correspond to internal addresses of the optical communication network 191x. The internal optical frame 193-2x is reached to the network node apparatus 195-2xvia routers 197-1x, 197-2x and 197-3x, which own an optical frame transfer function. The network node apparatus 195-2x removes a header of the received internal optical frame 193-2x (namely, optical frame is inverse-capsulated), sends out the acquired external IP packet 193-3x to a communication line 194-2x, and the IP terminal 192-2x receives an external IP packet 193-3x.
In accordance with the present invention, while IP addresses are applied to an IP telephone set, a media router (will be explained later), and various sorts of servers (these appliances will be referred to as “IP transmittable/receivable nodes” hereinafter), the IP packets are transmitted/received, so that the data may be exchanged in a mutual manner. These appliances will be referred to as “IP communication means”. FIG. 15 shows such an example that while an IP transmittable/receivable node 340-1 and another IP transmittable/receivable node 340-2 own IP addresses “AD1” and “AD2” respectively, an IP packet 341-1 having the transmission source IP address “AD1” and the destination IP address “AD2” is transmitted from the terminal 340-1 to the terminal 340-2. Also, both the IP transmittable/receivable nodes 340-1 and 340-2 receive the IP packet 341-2 along the opposite direction, so that the various sorts of data are mutually transmitted/received. A data portion from which the header of the IP packet is removed may also be called as a “payload”.
Next, there are provided with IP data multicast networks, IP base TV broadcast networks and, IP base movies distribution networks, while the multicast technique corresponding to one of the IP techniques is employed as the IP transfer networks. In the IP data multicast network, IP data such as electronic books and electronic newspapers is transferred from one distribution source to a plurality of destinations. In both the IP base TV broadcast networks and IP base movie distribution networks, which may function as IP sound (speech)/image networks, both TV sound data and TV picture (image) data are transferred (broadcasted) to a plurality of destinations. Referring now to FIG. 16, a multicast type IP transfer network 27-1 for transferring from one distribution source to a plurality of destinations will now be explained.
In FIG. 16, reference numerals 27-11 to 27-20 show routers. Each of these routers 27-11 to 27-20 holds a router-sort multicast table. This router-sort multicast table represents that a received IP packet should be transferred to a plurality of communication lines in accordance with multicast addresses contained in the received IP packets. In this embodiment, a multicast address designates “MA1”. In such a case that an IP packet 29-1 having the multicast address “MA1” is transmitted from an IP terminal 28-1, and then is reached via the router 27-11 to the router 27-18, this router 27-18 copies an IP packet 29-2, and transfers both an IP packet 29-3 and another IP packet 29-4 to a communication line by citating the router-sort multicast table held in the router 27-18. Also, the router 27-17 copies the received IP packet 29-3, and transfers an IP packet 29-5 to a communication line 29-17 by referring to the router-sort multicast table held in the router 27-18. Also, this router 27-17 transfers an IP packet 29-6 to a communication line 29-18 by referring to the router-sort multicast table. Since the router 27-19 owns no router-sort multicast table, the IP packet 29-4 directly passes through the router 27-19 to become another IP packet 29-7 which will be transferred to the router 27-14.
As indicated in FIG. 17, the router 27-17 inputs the IP packet 29-3 from the communication line 29-16, and makes such a confirmation that the transmission source IP address of the IP packet 29-3 is equal to “SRC1” and the destination IP address thereof is equal to the multicast address “MA1”. Since the output interfaces with respect to the multicast address “MA1” are designated as “IF-1” and “IF-2” in the multicast table 29-15, the router 27-17 copies the IP packet 29-3, and outputs the copied IP packet as an IP packet 29-5 to the communication line 29-17 whose output interface is equal to “IF-1”. Furthermore, the router 27-17 copies the IP packet 29-3, and then outputs the copied IP packet as an IP packet 29-6 to the communication line 29-18 whose output interface is equal to “IF-2”.
The router 27-12 copies the received IP packet 29-5, and then transfers the IP packet 29-8 to the IP terminal 28-2 and also the IP packet 29-9 to the IP terminal 28-3 by referring to the route-sort multicast table. Also, the router 27-13 copies the received IP packet 29-6, and then transfers the IP packet 29-10 to the IP terminal 28-4 and also the IP packet 29-11 to the IP terminal 28-5 by referring to the route-sort multicast table. Also, the router 27-14 copies the received IP packet 29-7, and then transfers the IP packet 29-12 to the IP terminal 28-6 and also the IP packet 29-13 to the IP terminal 28-7 by referring to the route-sort multicast table. In the case that the IP terminal 28-1 of the transmission source transfers a digital-formatted electronic book and a digital-formatted electronic newspaper to the IP transfer network 27-1, this IP transfer network 27-1 corresponds to an IP data multicast network which is employed so as to distribute an electronic book and an electronic newspaper, whereas the IP terminals 28-2 to 28-8 constitute IP terminals of users who purchase the electronic books and the electronic newspapers. In such a case that the IP terminal 28-1 of the transmission source is replaced by a TV broadcasting sound/image transmission apparatus so as to broadcast a TV program (both sound and image), the IP transfer network may constitute an IP base TV broadcast network, whereas the IP terminals 28-2 to 28-7 may constitute IP terminals equipped with TV reception functions for TV audiences.
In the above-described embodiment of the multicast system shown in FIG. 16, the IP terminal 28-1 constitutes the transmitter to transmit the multicast data, whereas the IP terminals 28-2 to 28-7 constitute the receivers to receive the multicast data. The multicast system with employment of such a method is utilized in the Internet and broadband LANs as a test purpose. However, in the multicast system, since any of the IP terminals may constitute the transmission source for transmitting the multicast data, the following risk may occur. That is, while a transmitter having a ill-intention appears, the transmitter continuously transmits multicast data in an endless manner, so that a network may be congested by the multicast data, and thus, a network function should be stopped. There is another risk that since multicast tables contained in routers are rewritten and/or a very large amount of data are supplied into routers in an endless manner, source routers are brought into overload conditions, and finally shut down. A large expectation is made of realizing such a multicast system with highly improved information securities, while employing the following security methods. That is, while a multicast data transmission source is limited, any of unfair users may be eliminated, and/or attacking of overload/shut-down of routers may be avoided.